Inactivation of Escherichia coli ATCC 25922 and Escherichia coli O157:H7 in Apple Juice and Apple Cider, Using Pulsed Light Treatment

Abstract

The main objective of this work was to evaluate the effectiveness of pulsed light (PL) treatment for the inactivation of Escherichia coli in liquids with different levels of clarity. Nonpathogenic E. coli ATCC 25922 and pathogenic E. coli O157: H7 were used as challenge organisms. Butterfield's phosphate buffer (BPB), tryptic soy broth (TSB), apple juice, and apple cider were used as substrates. The inoculated liquids were placed in a thin layer (1.3 mm) into glass chambers (23 by 53 by 11 mm) and exposed to PL doses of up to 13.1 J/cm2. PL treatments were performed in a Xenon RS-3000C PL unit, both in static mode and under turbulence. Survivors were determined by standard plate counting or the most-probable-number technique. For static treatments, reduction levels exceeding 8.5 log were obtained in BPB for all strains and reduction levels of about 3.5 log were obtained in TSB. For apple juice, inactivation levels of 2.66 +/- 0.10 log were obtained for E. coli ATCC 25922 and 2.52 +/- 0.19 log for E. coli O157:H7. In cider, inactivation levels of 2.32 +/- 0.16 log and 3.22 +/- 0.29 log were obtained for the nonpathogenic and pathogenic strains, respectively. Inactivation kinetics was characterized using the Weibull model. Turbulent treatments resulted in 5.76 +/- 0.06 log reduction in cider and 7.15 +/- 0.22 log reduction in juice, which satisfies the U.S. Food and Drug Administration requirement of 5-log reduction of E. coli. These results show promise for the use of PL for the effective reduction of E. coli in apple juice and cider.

Study of the inactivation of spoilage microorganisms in apple juice by pulsed light and ultrasound

“…PL application in fruit juices is very promising as some studies reflect its effectiveness as a decontamination technique. Among them, Sauer and Moraru (2009) studied the inactivation of Escherichia coli in apple juice (pH: 4.0; 11.3 Brix) and reported 2.7 log reductions (12.6 J/cm 2 , 1.3 mm layer liquid thickness) under static conditions. In addition, they observed up to 7.3 log reductions (8.8 J/cm 2 ) when generated turbulence in the liquid substrate during the PL treatment (3000 rpm, orbital shaker).…”

The role of pulsed light spectral distribution in the inactivation of Escherichia coli and Listeria innocua on fresh-cut mushrooms

“…Several studies have shown the ability of PL to inactivate Salmonella spp., Escherichia coli, E. coli O157:H7, Listeria monocytogenes and Listeria innocua in some products (Bialka & Demirci, 2008;Ozer & Demirci, 2006;Palgan et al, 2011;Sauer & Moraru, 2009;Uesugi & Moraru, 2009). The variability of results (2e8 log reductions) is most likely due to the different target microorganisms, the intensity of the treatment, and the properties of the substrates (MacGregor et al, 1998;Paskeviciute, Buchove, & Luksience, 2010;Sharma & Demirci, 2003;Woodling & Moraru, 2005).…”

Modeling the release of Escherichia coli from soil into overland flow under raindrop impact

“…coli ATCC 25922, a nonpathogenic surrogate of pathogenic E. coli O157: H7 ( Muirhead et al, 2006b;Salleh-Mack and Roberts, 2007;Sauer and Moraru, 2009 ), was grown in Tryptic Soy Broth (TSB; Becton, Dickinson and Company, Sparks, MD) for 18 h at 37 °C on a shaking table. Two milliliters of this culture was then mixed with 60 ml 1.08% potassium chloride (KCl) solution.…”